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Lung surfactant (LS) stabilizes the respiratory surface by forming a film at the alveolar air-liquid interface that reduces surface tension and minimizes the work of breathing. Typically, this surface-active agent has been isolated from animal lungs both for research and biomedical applications. However, these materials are constituted by complex membranous architectures including surface-active and inactive lipid/protein assemblies. In this work, we describe the composition, structure and surface activity of discrete membranous entities that are part of a LS preparation isolated from bronchoalveolar lavages of porcine lungs. Seven different fractions could be resolved from whole surfactant subjected to sucrose density gradient centrifugation. Detailed compositional characterization revealed differences in protein and cholesterol content but no distinct saturated:unsaturated phosphatidylcholine ratios. Moreover, no significant differences were detected regarding apparent hydration at the headgroup region of membranes, as reported by the probe Laurdan, and lipid chain mobility analysed by electron spin resonance (ESR) in spite of the variety of membranous assemblies observed by transmission electron microscopy. In addition, six of the seven separated LS subfractions formed similar, essentially disordered-like, interfacial films and performed efficient surface activity, under physiologically relevant conditions. Altogether, our work show that a LS isolated from porcine lungs is comprised by a heterogenous population of membranous assemblies lacking freshly secreted unused LS complexes sustaining highly dehydrated and ordered membranous assemblies as previously reported. We propose that surfactant subfractions may illustrate intermediates in sequential structural steps within the structural transformations occurring along the respiratory compression-expansion cycles.

Pitavastatin is a statin drug that, by competitively inhibiting 3-hydroxy-3-methylglutaryl-coenzyme A reductase, can lower serum cholesterol levels of low-density lipoprotein (LDL) accompanied by side effects due to pleiotropic effects leading to statin intolerance. These effects can be explained by the lipophilicity of statins, which creates membrane affinity and causes statin localization in cellular membranes. In the current report, the interaction of pitavastatin with POPC model membranes and its influence on the membrane structure were investigated using H, H and P solid-state NMR spectroscopy. Our experiments show the average localization of pitavastatin at the lipid/water interface of the membrane, which is biased towards the hydrocarbon core in comparison to other statin molecules. The membrane binding of pitavastatin also introduced an isotropic component into the 31P NMR powder spectra, suggesting that some of the lamellar POPC molecules are converted into highly curved structures., Highlights • Solid-state NMR spectroscopy shows pitavastatin effect on the bilayer •Pitavastatin lowers the POPC order parameters •Pitavastatin localize in the upper chain of the POPC bilayer •Isotropic membrane phases are observed in the presence of pitavastatin

Lung surfactant (LS) is an outstanding example of how a highly regulated and dynamic membrane-based system has evolved to sustain a wealth of structural reorganizations in order to accomplish its biophysical function, as it coats and stabilizes the respiratory air-liquid interface in the mammalian lung. The present review dissects the complexity of the structure-function relationships in LS through an updated description of the lipid-protein interactions and the membrane structures that sustain its synthesis, secretion, interfacial performance and recycling. We also revise the current models and the biophysical techniques employed to study the membranous architecture of LS. It is important to consider that the structure and functional properties of LS are often studied in bulk or under static conditions, in spite that surfactant function is strongly connected with a highly dynamic behaviour, sustained by very polymorphic structures and lipid-lipid, lipid-protein and protein-protein interactions that reorganize in precise spatio-temporal coordinates. We have tried to underline the evidences available of the existence of such structural dynamism in LS. A last important aspect is that the synthesis and assembly of LS is a strongly regulated intracellular process to ensure the establishment of the proper interactions driving LS surface activity, while protecting the integrity of other cell membranes. The use of simplified lipid models or partial natural materials purified from animal tissues could be too simplistic to understand the true molecular mechanisms defining surfactant function in vivo. In this line, we will bring into the attention of the reader the methodological challenges and the questions still open to understand the structure-function relationships of LS at its full biological relevance.

Polyethersulfone (PES) is a polymeric material with good chemical stability, mechanical strength, and thermal stability. It has been used in various separation processes such as gas separation, water filtration, and osmotic power generation. Membrane performance of PES hollow fibers can be controlled by manipulating the membrane fabrication process, e.g., dope/bore fluid preparation, spinning conditions, and postspinning treatments. The effects of factors such as the compositions and flow rates of dope and bore fluid, air gap, take-up speed, drying method, etc., on membrane structure and properties are presented. In addition, desirable properties of PES hollow fiber membranes are discussed for applicable separation processes.

In recent years, lack of access to safe and pure water is one of the most critical issues in the world. Membrane technology is a promising technique for water treatment and is expected to play an increasingly important role in treatment areas such as drinking water, brackish and seawater desalination, and wastewater in the upcoming years, both on a domestic and on an industrial scale. Polymers and polymeric composite-based materials have been widely used as commercial membrane materials due to their wide range of advantages in terms of structure, morphology, physiochemical, and filtration characteristics. Currently, the usage of smart materials for polymeric membrane synthesis has intensified the membrane research toward a new class of membranes development and their applications in various fields. These stimuli-responsive smart materials could be designed to alter the membrane structure and physicochemical properties such as hydrophilicity, porosity, charge density, thermal and mechanical stability, etc. This chapter aims to summarize the recent scientific and technological advances of stimuli-responsive smart polymeric membrane materials for water and wastewater treatment applications. Various unique attributes of smart responsive materials, challenges, and future research directions in developing smart polymeric membranes are also discussed.

Impact of different lipids on membrane structure/lipid order is critical for multiple biological processes. Laurdan microscopy provides a unique tool to assess this property in heterogeneous biological membranes. This review describes the general principles of the approach and its application in model membranes and cells. It also provides an in-depth discussion of the insights obtained using Laurdan microscopy to evaluate the differential effects of cholesterol, oxysterols and oxidized phospholipids on lipid packing of ordered and disordered domains in vascular endothelial cells.

In this study, novel nanofiber based-hybrid proton conducting membranes for polymer electrolyte membrane (PEM) fuel cells were fabricated via electrospinning method using sulfonated silica particles (S-SiO2) as a functional additive. Here, poly(vinylidene fluorideco-trifluoroethylene) (P(VDF-TrFE)) was used as the carrier polymer during electrospinning step for the fabrication of PEM fuel cell membrane structure for the first time in literature. The effect of electrospinning conditions, i.e. namely, solvent, carrier polymer, electrospinning voltage, relative humidity, and flow rate on the uniformity of the resultant electrospun mats, and the average fiber diameter, respectively, were investigated in detail. Furthermore, electrospinning was conducted with poly(vinylidene fluoride) (PVDF) as the carrier polymer to compare with (P(VDF-TrFE)) as well. S-SiO2 particles were homogeneously distributed along the carrier polymer without any noticeable bead formation. After electrospinning, fiber mats were transformed into dense membranes via hot-pressing and subsequent Nafion (R), water uptake and mechanical strength of the hybrid membranes were examined and reported as well. Consequently, hybrid membrane with P(VDF-TrFE) carrier exhibited a superior proton conductivity (102 mS/cm) benchmarked with PVDF carrier polymer containing membrane (43 mS/cm) and solution casted Nafion (R) membrane (95 mS/cm) at the same conditions. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Hybrid membranes based of polyphenylene oxide matrix and star macromolecules (up to 5 wt%) containing six polystyrene and six poly-2-vinylpyridine arms attached to a common fullerene C60 center were prepared and successfully used for pervaporation separation of acetic acid – water mixtures. The peculiarities of the hybrid membrane structure and properties were studied by small-angle neutron scattering in two states (dry and swollen in deuterated acetic acid). It was established that star macromolecules are non-uniformly distributed in the matrix and form aggregates; they increase in the size up to ~60% during swelling of membranes in deuterated acetic acid. In pervaporation, the total flux through the membrane rises with increasing both the star macromolecule content in membrane and water concentration in the feed. Separation factor reaches its greatest value when the hybrid membrane contains 5 wt% star macromolecules. Keywords: Pervaporation, Neutron scattering, Membrane, Polyphenylene oxide, Star macromolecules, Acetic acid – water mixture

Currently, photocatalytic materials-based membranes have become one of the efficient and green approaches for the elimination of hazardous pollutants in water and wastewater treatment. In this case, the highly active photocatalyst incorporated within the membrane structure or on the membrane surface imparts additional functionalities to the conventional membranes as well as to overcome its drawback in separating the photocatalyst from the reaction system. This chapter emphasizes various fabrication techniques of photocatalytic materials-based membranes which includes thin film or hollow fibers membrane. Several factors and parameters that affect the morphological and structural properties of photocatalytic materials-based membranes, related to its desirable properties, will be discussed in detail. Recent applications of photocatalytic materials-based membranes in treating various hazardous pollutants in water and wastewater treatment will also be discussed.

In this chapter, we summarize some important parameters regarding the proton exchange membrane (PEM) in a direct methanol fuel cell (DMFC) system. The PEM mainly consists of a solid polymer that can be either natural or synthetic. Synthetic polymers are much easier to handle due to their natural, man-made production. The purpose is to present the type of membrane structure that is commonly governed in DMFC applications. Other than that, membrane fabrication methods, membrane characterization, and separation mechanisms that occur inside the polymer matrix are disclosed in this chapter. The potential applications of DMFC in various field is also explored. Therefore, by analyzing all of the above concerns, it was assumed that the understanding of DMFC systems could be further clarified, which is not only restricted to dense membranes, but also to porous membranes.

The selection of nanocomposite membrane fabricating process depends on the characteristics of the chosen polymer and nanofiller as well as the desired nanocomposite membrane structure. The fabrication techniques include phase inversion, stretching, track etching, interfacial polymerization and electrospinning. The nanocomposite membranes produced from these techniques can be in the form or symmetric or asymmetric membranes. It is difficult to make direct comparison among these techniques because the structure, properties and performance of the membranes formed are strongly influenced by the materials and operating parameters involved during the fabrication process. In terms of gas separation nanocomposite membrane fabrication, most of the preparations are still centred around phase inversion techniques. Phase inversion has been widely used for the one-step fabrication of mixed matrix membrane or for the preparation of polymeric substrate of multilayer nanocomposites membranes.

[EN] After long-term electrodialysis, cleaning the membranes is crucial to extend their lifetime. In this work, we evaluate the effects of a three-stage chemical cleaning on electrochemical and structural properties of anion- and cation-exchange membranes. Membranes used in the electrodialytic treatment of a synthetic effluent from the cyanide-free brass electrodeposition were cleaned using 0.1, 0.5 and 1.0 mol.L-1 NaOH solutions. The electrochemical behavior of the membranes was evaluated after each cleaning step by chronopotentiometry. Additionally, changes in the membrane structure and composition were analyzed by FTIR-ATR and SEM/EDS. While the membranes undergo a decline in some electrochemical features after the electrodialysis process, the cleaning with 0.1 mol.L-1 NaOH showed to be the most effective in recovering the properties characteristic of the virgin membranes: the limiting current density increased by 84% after the cleaning, whereas the ohmic and overlimiting resistances decreased by 47% and 55%, respectively. In contrast, the 0.5 and 1.0 mol.L-1 NaOH solutions degraded the membranes and reduced their fraction of conducive area, especially for the anion-exchange one. This favored fouling/scaling occurrence, as noticed by a prominent increase in the potential drop of the anion-exchange membrane. FTIR-ATR and SEM/EDS analyses confirmed fouling/scaling, as well as degradation of the ion-exchange membranes., The authors gratefully acknowledge the financial support given by funding agencies CNPq (Process 141346/2016-7) and CAPES (Process 88881.190502/2018-01). This study was financed in part by the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior -Brasil (CAPES) -Finance Code 001.

Microporous zeolite membranes have great potential in many applications. The structures of zeolite membrane are summarized first in terms of channel dimensionality and pore size. In situ synthesis and secondary growth are two methods commonly used for the preparation of zeolite membranes. The zeolite crystals can grow in hydrothermal or dry-gel conditions using oven or microwave heating. The synthesis of oriented and ultrathin zeolite layers, which is the ideal morphology to obtain high performance, is discussed in detail. The topology, morphology, pore structures, and defects are characterized by many instruments and analyzed to better understand and control the membrane's quality. Finally, applications of zeolite membranes in separation or catalyst reactor are simply reviewed.

In last decades, in comparison with traditional chemical separation processes, membrane separation is much simpler and more efficient. An ideal membrane for molecular separation should be as thin as possible to maximize its solvent flux, mechanically robust to prevent it from fracture, and have well-defined pore sizes to guarantee its selectivity. Graphene is an excellent platform for developing size-selective membranes because of its atomic thickness, high mechanical strength, and chemical inertness. In this chapter, we review the recent advancements on the fabrication of nanoporous graphene membranes and graphene oxide membranes (GOMs) for molecular separation. The methods of fabricating these membranes are summarized, and the mechanisms of molecular separation based on these two types of graphene membranes are compared. The challenges of synthesizing nanoporous graphene membranes and engineering the performances of GOMs are discussed.

The plasma membrane forms the physical barrier between the cytoplasm and extracellular space, allowing for biochemical reactions necessary for life to occur. Plasma membrane damage needs to be rapidly repaired to avoid cell death. This relies upon the coordinated action of the machinery that polarizes the repair response to the site of injury, resulting in resealing of the damaged membrane and subsequent remodeling to return the injured plasma membrane to its pre-injury state. As lipids comprise the bulk of the plasma membrane, the acts of injury, resealing, and remodeling all directly impinge upon the plasma membrane lipids. In addition to their structural role in shaping the physical properties of the plasma membrane, lipids also play an important signaling role in maintaining plasma membrane integrity. While much attention has been paid to the involvement of proteins in the membrane repair pathway, the role of lipids in facilitating plasma membrane repair remains poorly studied. Here we will discuss the current knowledge of how lipids facilitate plasma membrane repair by regulating membrane structure and signaling to coordinate the repair response, and will briefly note how lipid involvement extends beyond plasma membrane repair to the tissue repair response.

Polymer composite membrane–based gas separation is still a growing area as efforts for accurate tracing of correlations between thin film composite/membrane structure and its gas transport properties are yet to be complete. This type of gas separation has immense advantages such as low cost, easy handling, light weight, and excellent flexibility. In addition, the greatest advantage of this method is the wide variety of polymers available in the market, which enables the selection of the apt membrane material for separating a particular gas. This field is evolving very rapidly as novel techniques based on mixed matrix composite membranes and other membrane-based hybrid structures are being employed. The key to success is obviously in understanding the relationship between the structure of polymer membrane and the transport through it. This chapter sheds some light on the studies conducted in this regard so far. It also discusses some of the recent findings made in the realm of polymer membrane–based gas transport.

In this chapter, the design and analysis of two special types of structures: tensile and tensegrity structures are explained. It starts with the introduction of tensile structure, including different membrane materials, different types of support. This is followed by discussion of major loadings need to be considered for tensile structural. Then, the general design considerations are illustrated which covers some of the important design issues such as wrinkling of the membrane. Detailed analysis theories for form finding and static analysis are illustrated. They are nonlinear finite element method, force density method, and dynamic relaxation method. The way to model membrane structure in ANSYS and Abaqus are also described. In the final two sections of this chapter it covers the topic of tensegrity structures. Design and analysis methods are examined. The analysis methods for tensegrity structure are demonstrated using Georgia Dome as a prototype, which is modeled using design orientated program SAP2000.

This chapter introduces water transport characteristics through different types of polymer membranes in membrane distillation (MD), forward osmosis (FO), and pressure-retarded osmosis (PRO) processes. It starts by briefly explaining the mechanisms of the three membrane processes. It then elaborates the major factors influencing water transport through MD, FO, and PRO membranes as well as the empirical models that describe these factors. Extensive discussion of the driving force, membrane structure, operation conditions, and feed water quality is included to reveal their relationship with water transport. At the end of the chapter, typical applications of MD, FO, and PRO are introduced. Hot topics in the three processes, challenges, and future research prospects are also presented.

A novel approach to enhance membrane performance using electrospinning fabrication technique for recovery of heavy metals using air-gap membrane distillation is described. Accordingly, a comprehensive study was accomplished to fabricate a unique electrospun dual-layer membrane (ESD) with an upper superhydrophobic layer and hydrophobic electrospun support layer and compare with a superhydrophobic electrospun single layer membrane (ESS). Superhydrophobic alumina nanoparticles (Al2O3) were embedded in a low polymer concentration of polyvinylidene fluoride (PVDF) to produce superhydrophobic ESS and top layer of ESD using electrospinning technique, while a mat with different concentrations of PVDF were used as hydrophobic electrospun support layer. In this study, dual layer membranes were fabricated in two sets. In the first set, layer thickness was varied by changing the spinning volume of the top and support layer with maintain total spinning volume, while in the second set the fibre diameter of the support layer was varied by changing the polymer concentration. Moreover, the electrospun membranes were characterized in terms of membrane performance such as: permeate flux, heavy metal rejection and energy consumption; wettability performance such as liquid entry pressure (LEP), and water contact angle (WCA); membrane structure such as mean with maximum pore size and porosity; membrane integrity such as mechanical and thermal integrity. The heavy metal rejection was >99% for all single and dual layer membranes when filtering artificial wastewater (Pb, Cd, Cr, Cu, Ni). When compared with single layer electrospun membrane made from spinning 16 ml PVDF, dual layer membrane made from the same spinning volume exhibited some improvement, such as higher permeate flux above 23 l/m2∙h (LMH) when filtering 2500 ppm concentration heavy metal feed water. Additionally, both sets of dual layer membrane demonstrated better mechanical performance and slight reduction of LEP compared with single layer electrospun membrane.

Membranes assembled by two-dimensional (2D) nanosheets have high potential for advanced molecular separation. The intercalation of nanomaterials into the laminar membrane is a promising strategy to control the nanochannel structure. We present 2D niobate nanosheet (NbN)-Graphene oxide (GO) composite membranes fabricated by simple vacuum filtration. The effect of the weight ratio of NbN/GO on the membrane structures and performances is investigated. The NbN-rich membranes have a more stable structure in the wet condition and a membrane structure with a larger channel size compared with GO-rich membranes. Especially, NbN55-GO45 (weight ratio of NbN/GO = 55/45) shows a superior water permeability of 20 L m−2 h−1 bar−1, which is around 6 times higher than an NbN membrane (NbN100) and 2 times higher than a GO membrane (GO100), while maintaining good rejection abilities of an anionic dye (nearly 100% for Evans blue) and salt (60% for Na2SO4). Different models for the water pathway through nanochannels can be classified according to the composite ratio of the NbN-GO membranes.

In this paper, a vibration testing and health monitoring system based on an impulse response excited by laser is proposed to detect damage in membrane structures. A high power Nd: YAG pulse laser is used to supply an ideal impulse to a membrane structure by generating shock waves via laser-induced breakdown in air. A health monitoring apparatus is developed with this vibration testing system and a damage detecting algorithm which only requires the vibration mode shape of the damaged membrane. Artificial damage is induced in membrane structure by cutting and tearing the membrane. The vibration mode shapes of the membrane structure extracted from vibration testing by using the laser-induced breakdown and laser Doppler vibrometer are then analyzed by 2-D continuous wavelet transformation. The location of damage is determined by the dominant peak of the wavelet coefficient which can be seen clearly by applying a boundary treatment and the concept of an iso-surface to the 2-D wavelet coefficient. The applicability of the present approach is verified by finite element analysis and experimental results, demonstrating the ability of the method to detect and identify the positions of damage induced on the membrane structure.

In this article, the materials and methods for the preparation of various types of membranes are described. The article will highlight the preparation of porous and dense (symmetric and asymmetric) membranes made from polymeric and inorganic material. The preparation of composite membranes will also be discussed. The use of green solvents to develop environmentally friendly preparation methods is presented. Novel membranes designed for recently developed membrane operations, including membrane emulsification and biohybrid multifunctional membranes, are also introduced.

Analysis of peptide/protein–membrane interactions is central to delineating the regulatory mechanisms of many membrane-mediated biochemical processes associated with receptor signaling, molecular transport, membrane trafficking, cell–cell communication, organelle dynamics, membrane destabilization by cytotoxic toxins, and antimicrobial peptides. Among a wide-range of biophysical methods for studying the membrane interaction, dual polarization interferometry (DPI) combines supported lipid bilayers and a highly sensitive optical waveguide interferometer. The unique features of evanescent field sensing and optical phase difference measurement in DPI thus provide quantitative analysis of changes in molecular mass and molecular packing order of the membrane. The use of simpler membrane model systems to mimic the complex native biomembrane demands robust methods to prepare stable lipid bilayers particularly in terms of reproducible structural organization. With these unique features, DPI has been used to screen key parameters to control the successful formation of lipid bilayers via vesicle fusion and to characterize biomolecule/membrane interactions simultaneously with the reciprocal impact of the molecular binding on the destruction of membrane structure throughout the dynamic association–dissociation process. This multiplex analysis of the dynamic changes in lipid organization and molecular mass has provided new insight into the molecular mechanisms of membrane-active peptides and proteins especially in relation to changes in bilayer structure associated with the biomembrane binding and disruption.

The design of new membranes and the improvement of existing ones rest significantly on the understanding of the mechanisms of separation in the interior of the membrane material. In turn, these mechanisms depend heavily on the internal structure and, more specifically, on the spatial distribution of the chemical and physical constituents of the membrane material. It is exactly this interrelationship between structure and transport that several serious modeling efforts have focused on, with rapidly increasing efficiency over the last decade for polymeric, inorganic, and hybrid membranes. This article provides a review of relevant research efforts, accomplishments, and trends in the direction of membrane material and transport modeling along with some new developments and ideas for future work.

The phage shock protein (Psp) response maintains integrity of the inner membrane (IM) in response to extracytoplasmic stress conditions and is widely distributed amongst enterobacteria . I ts central component PspA , a member of the IM30 peripheral membrane protein family , acts as a major effector of the system through its direct association with the IM . Under non - stress con ditions PspA also negatively regulates its own expression via direct interaction with the AAA+ ATPase PspF. PspA has a counterpart in cyanobacteria called Vipp1 , which is implicated in protection of the thylakoid membrane s . PspA’s and Vipp1’s conserved N - terminal regions contain a putative a mphipathic h elix a (AHa) required for membrane binding . An adjacent amphipathic helix b (AHb) in PspA is required for imposing negative control upon PspF . Here, p urified peptides derived from the putative AH regions o f PspA and Vipp1 were used to directly probe their effector and regulatory function s . We observed direct membrane - binding of AHa derived peptides and an accompanying change in secondary structure from unstructured to alpha - helical establishing them as bona fide membrane - sensing AH’s. The p eptide - b inding specificit ies and the ir effects on membrane stability depend on membrane anionic lipid content and stored curvature elastic stress , in agreement with ful l length PspA and Vipp1 protein functionalities. AHb of PspA inhibited the ATPase activity of PspF demonstrating its direct regulatory role. These findings provide new insight into the membrane binding and function of PspA and Vipp1 and establish that synthetic peptides can be used to probe the structure - fu nction of the IM30 protein family .

Little is known about the effects of altering sphingolipid (SL) acyl chain structure and composition on the biophysical properties of biological membranes. We explored the biophysical consequences of depleting very long acyl chain (VLC) SLs in membranes prepared from lipid fractions isolated from a ceramide synthase 2 (CerS2)-null mouse, which is unable to synthesize C22–C24 ceramides. We demonstrate that ablation of CerS2 has different effects on liver and brain, causing a significant alteration in the fluidity of the membrane and affecting the type and/or extent of the phases present in the membrane. These changes are a consequence of the depletion of VLC and unsaturated SLs, which occurs to a different extent in liver and brain. In addition, ablation of CerS2 causes changes in intrinsic membrane curvature, leading to strong morphological alterations that promote vesicle adhesion, membrane fusion, and tubule formation. Together, these results show that depletion of VLC-SLs strongly affects membrane biophysical properties, which may compromise cellular processes that critically depend on membrane structure, such as trafficking and sorting.

The first half of this book focused on the composition and structure of biological membranes (Part I. Membrane Composition and Structure). The last half of the book will concentrate on membrane function (Part II. Membrane Biological Functions). Since biological membranes are such extremely complex entities, composition, structure and, function are so completely integrated that it is impossible to discuss one aspect in the absence of the other two. This last part of the book will first investigate membrane biogenesis with discussion of the following topics: Chapter 14 . Membrane Biogenesis: Fatty Acids Chapter 15 . Membrane Biogenesis: Phospholipids, Sphingolipids, Plasmalogens and Cholesterol Chapter 16 . Membrane Biogenesis: Proteins

Understanding membrane structure and function is one of the major unresolved problems in life science. Membranes are intimately involved in almost all biological processes including: establishing and maintaining trans-membrane gradients; compartmentalizing biochemical reactions into distinct functional domains; controlling transport into and out of cells; inter- and intra-cellular communication; cell–cell recognition; and energy transduction events. What makes biological membranes so difficult to study is their small size (

Advances in recent studies of the bordered pit membrane structure and its association with cavitation resistance were reviewed, as well as to summarize our current knowledge of the structure of bordered pit membranes. Recent studies have shown that the structure of bordered pit membranes in angiosperms is more complicated than has been acknowledged previously. Linking structural studies of intervessel pits with physiological studies gave new insight into the mechanisms of how intervessel pit membranes regulate the water flow and the progression of cavitation in vessel-bearing angiosperms. New findings have been also reported regarding the fine structure of pit membranes between imperforate tracheary elements. Torus, its related structures and perforated pit membranes have been recorded in a wide range of taxa from basal to derived groups in angiosperms. Attempts have been also made to clarify the relationship between the micromorphological characters and cavitation resistance for intertracheary pit membranes with distinction of torus and margo in conifers.